Someone apparently needed one of mine more than me..... they we're very tight and took a little red knuckles to unscrew so i'm sure it didn't " fall out " while trailering. I'f any of you guys have a spare or a set to sell i'm ready to buy. I can't sail until i get one as its on the rear of the starboard hull and will full with water lol.The port is 5" but the lid is roughly about 4 3/4" .....thanks guys!Tim